A storage subsystem manages a plurality of storage area groups classified according to the attribute of a plurality of storage areas provided by a plurality of storage devices. Further, a technique called thin provisioning or dynamic provisioning is provided, in which at least one storage area included in the plurality of storage areas is allocated according to a write request from a host computer to at least one address included in a plurality of addresses in a virtual volume.
Patent literature 1 discloses an art of providing a plurality of virtual volumes, wherein in accordance with the access condition of at least one address in the logical volume, the data written to the at least one address by the write request is migrated from the at least one storage area included in one of the multiple storage area groups to at least one storage area in another storage area group included in the multiple storage area groups.